1. Field of the Invention
The present invention relates to the field of displaying technology, and in particular to an active matrix organic light emitting display (AMOLED) backplane structure and a manufacturing method thereof.
2. The Related Arts
An organic light emitting display (AMOLED) is a displaying technique having a extremely prosperous future. An OLED display device shows excellent displaying performance and also possesses various advantages, such as being self-luminous, simple structure, being ultra-thin and light, fast response speed, wide view angle, low power consumption, and being capable of achieving flexible displaying and is thus regarded as a “dream display” that attracts the attention of major display manufacturers and becomes the mainstream of the three-generation display devices of the field of display technology.
The OLED display devices are classified, according to the way of driving, into two categories, including passive matrix OLED (PMOLED) and active matrix OLED (AMOLED), namely direct addressing thin-film transistor (TFT) and matrix addressing. Among them, AMOLED is of an active displaying type, having a high light emission efficiency and being commonly used for manufacturing high definition large-sized display devices.
A conventional AMOLED backplane generally comprises multiple pixels arranged in an array. Each of the pixels comprises three sub-pixels of red, green, and blue. As shown in FIG. 1, the conventional AMOLED backplane comprises a first thin-film transistor T10, a capacitor C10, and a second thin-film transistor T20 formed in an area thereof corresponding to each of sub-pixel. A pixel electrode 600 is formed on a planar surface of a planarization layer 500. In the area of a sub-pixel, due to the occupation of the first thin-film transistor T10, the capacitor C10, the second thin-film transistor T20 and related wiring of the sub-pixel area, only a smaller amount of area (namely the aperture ratio) is preserved for the pixel electrode 600 for effective displaying. In other words, the area of light emission is smaller. Consequently, to achieve a desired luminous brightness in a unit ear, an increased current density is necessary. This leads to accelerated aging of the OLED material. Further, comparison among the three sub-pixels of red, green, and blue, generally, the blue sub-pixel has a lower light emission efficiency and as a consequence, the blue sub-pixel must be provided with a larger area to ensure the illumination and lifespan of the blue sub-pixel. Relatively, the red and green sub-pixels have smaller areas. This leads to problems of design difficulty and reduction of resolution.
To increase an effective displaying area, Chinese Patent Application No. CN201410155846.2 discloses an OLED display device, As shown in FIG. 2, the disclosed OLED display device comprises a base plate 302. A planarization layer 304 is arranged on the base plate 302. Multiple curved sections 304a are arranged on the planarization layer 304 in a manner of being spaced from each other. The curved sections 304a comprise multiple corrugated surfaces. A cross-section of the curved sections 304a, in entirety thereof, has an arc contour. The planarization layer 304 comprises multiple light emission units 306 formed thereon and each of the light emission units 306 is set on each of the curved sections 304a and has a configuration corresponding to the curved section 304a. The light emission units 306 comprise a first electrode 306a, a light emissive structure 306b, and a second electrode 306c. With the arrangement of the planarization layer 304 that includes curved sections 304a, formation of light emission units 306 having curved surfaces can be achieved to help increase light emission areas of the light emission units 306 thereby improving luminous brightness. However, in the above-discussed patent document, the planarization layer 304 and the curved sections 304a are formed at the same time and there would be a potential risk that defects may occur in GD at abrupt change sites and thus affect the lifespan of the OLED. In addition, manufacturing of the curved sections 304a requires the use of gray scale masks; this increases the difficulty of the process and leads to deterioration of yield rate.